
X24C01A 
3 
Figure 1.  Data Validity 
Figure 2.  Definition of Start and Stop 
Stop Condition  
All communications must be terminated by a stop 
condition, which is a LOW to HIGH transition of SDA 
when SCL is HIGH. 
The stop condition is also used by the X24C01A to place 
the device into the standby power mode after a 
read sequence. A stop condition can only be issued after the 
transmitting device has released the bus. 
Acknowledge  
Acknowledge is a software convention used to indicate 
successful data transfers. The transmitting device will 
release the bus after transmitting eight bits. During the ninth 
clock cycle the receiver will pull the SDA line LOW 
to acknowledge that it received the eight bits of data. 
Refer to Figure 3. 
The X24C01A will respond with an acknowledge after 
recognition of a start condition and its slave address. If 
both the device and a write operation have been selected, 
the X24C01A will respond with an acknowledge 
after the receipt of each subsequent eight bit word. 
In the read mode the X24C01A will transmit eight bits of data, 
release the SDA line and monitor the line for an 
acknowledge.  If  an  acknowledge  is  detected  and  no stop 
condition is generated by the master, the X24C01A 
will continue to transmit data. If an acknowledge is not 
detected, the X24C01A will terminate further data trans- 
missions. The master must then issue a stop condition to 
return the X24C01A to the standby power mode and 
place the device into a known state. 
Figure 3.  Acknowledge Response From Receiver 
SCL 
SDA 
DATA STABLE 
DATA 
CHANGE 
3841 FHD F05 
3841 FHD F06 
3841 FHD F07 
SCL FROM 
MASTER 
DATA 
OUTPUT 
FROM 
TRANSMITTER 
1 
8 
9 
DATA 
OUTPUT 
FROM 
RECEIVER 
START 
ACKNOWLEDGE 
SCL 
SDA 
START BIT 
STOP BIT